Semiconductor device structures with capacitor containers and contact apertures having increased aspect ratios

ABSTRACT

Semiconductor device structures and methods of making such structures that include one or more etched openings (e.g., capacitor containers and/or contact apertures) therein with increased height-to-width ratios are provided. The structures of the present invention are formed by successive layer deposition wherein conventional patterning techniques may be utilized in a stepwise fashion as the height of the structure is increased. Further provided is a self-aligning interconnection structure which may be used to substantially vertically align openings formed in successively deposited, vertically placed structural layers of a semiconductor device. The interconnection structure utilizes a cap-and-funnel model that self-aligns to the center plane of an opening in a first structural layer and also substantially prevents subsequently deposited material from entering the opening.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of application Ser. No.10/329,913, filed Dec. 26, 2002, pending.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the fabrication ofsemiconductor device structures. More particularly, the presentinvention relates to semiconductor device structures with capacitorcontainers, contact apertures, or other openings therein that haveincreased height-to-width ratios. Further, the present invention relatesto methods of making semiconductor device structures having capacitorcontainers, contact apertures, or other openings therein with increasedaspect ratios.

[0004] 2. Background of the Related Art

[0005] In computer semiconductor devices, such as dynamic random accessmemory (DRAM) semiconductor device modules, the memory capacitorstypically are formed inside containers, such as phosphosilicate glass(PSG), borosilicate glass (BSG), or borophosphosilicate glass (BPSG)containers, through etching techniques. An exemplary partiallyfabricated semiconductor device structure 10 is schematicallyillustrated in FIG. 1. A conductive plug 11 located between neighboringconductive structures 12, such as transistor gate stacks, formselectrical contact with an active device region 14 of a semiconductorsubstrate 16, e.g., a silicon (Si) wafer. A planarized insulating layer18, such as a BPSG layer, surrounds the conductive structures 12. Theconductive plug 11 is formed within an opening through the insulatinglayer 18. A structural layer 20 having a height, H, overlies theinsulating layer 18 and may also be formed of BPSG or similar material.A capacitor container 22 having a width W is formed in the structurallayer 20, generally by etching the structural layer 20 through aphotomask (not shown). The capacitor container 22 is a generallycylindrical cavity formed contiguous with the conductive plug 11 (or anactive device region 14 of the semiconductor substrate 16) and includessidewalls 24 that extend to an opening in the insulating layer 18.

[0006] Typically, etching techniques include the depositing, masking andpatterning of protective layers, such as photoresists (not shown), whichact as templates and may be patterned to form photomasks (not shown)through which structures in the desired layer (e.g., structural layer20) of a semiconductor device structure may be defined. Wet etch or dryetch techniques may be employed to define semiconductor devicestructures. In contrast with wet etch techniques, techniques involvingdry etch, including, without limitation, glow-discharge sputtering, ionmilling, reactive ion etching (RIE), reactive ion beam etching (RIBE),plasma etching, point plasma etching, magnetic ion etching, magneticallyenhanced reactive ion etching, plasma enhanced reactive ion etching,electron cyclotron resonance and high-density plasma etching, arecapable of etching in a substantially anisotropic fashion. This meansthat the target area of a substrate is etched primarily in asubstantially vertical direction relative to the exposed, or active,surface of the substrate. Thus, such dry etch techniques are capable ofdefining structures with substantially vertical sidewalls. Consequently,such dry etch techniques are capable of accurately reproducing thefeatures of a photomask. Due to a trend in semiconductor fabricationprocesses toward decreased dimensions of structures on semiconductordevices, dry etching is often desirable for defining structures uponsemiconductor device substrates.

[0007] Concurrent with ever-decreasing die sizes, the width (ordiameter) of capacitor containers must be reduced. However, DRAMcapacitors of sufficient size to store and maintain the requisite amountof charge to permit the necessary refresh time must still be provided.

[0008] Accordingly, it has been proposed to fabricate capacitorcontainers of dielectric materials having higher dielectric constantsthan materials typically utilized. However, a change in material wouldcause a substantial interference with existing semiconductormanufacturing processes and, thus, such solution is undesirable.

[0009] As capacitance is a function of the surface area of thecapacitor, tremendous efforts have been made in the semiconductorindustry to maintain or increase the surface areas of capacitors,despite a decrease in the widths of capacitor containers. By increasingthe surface area of the container, and thus an electrode associatedtherewith, capacitance charge may be maintained, or even increased, fora capacitor container having a reduced width. Typically, surface areasof capacitors are increased by the formation of an enhanced surface arealayer, such as a hemispherical grain (HSG) polysilicon layer, on theinterior surface of the capacitor container. The HSG polysilicon layerincreases the surface area of the capacitor container due to thethree-dimensional hemispherical configuration and convolutions of thesilicon. While this technique creates a capacitor container with anincreased surface area relative to a similarly sized capacitor containerthat is not lined with HSG polysilicon, surface area is still limited bythe confines of the capacitor container structure. That is, an HSGpolysilicon-lined capacitor container having a smaller width will have alesser surface area than an HSG polysilicon-lined capacitor containerhaving a larger width, assuming the two capacitor containers have asubstantially equivalent height.

[0010] A further approach to enhancing the total surface areas ofcapacitor containers involves modifying the geometrical layout of thecontainers. However, the usefulness of this technique is similarlylimited by the confines of the capacitor container in that a particulargeometrical layout in a capacitor container having a smaller width willhave a lesser surface area than a similar geometrical layout in acapacitor container having a larger width and a substantially equivalentheight.

[0011] As surface area is a function not only of the width of thecapacitor container but also of the height thereof, a decrease in widthaccompanied by a proportional increase in height theoretically wouldprovide a capacitor container having identical surface area. However,there are limitations to forming a large height-to-width ratio usingknown etching techniques due to the limitations of selective etching.For instance, preservation of the surface underlying the etched layermay become compromised if the aspect ratio of the capacitor container istoo great.

[0012] As shown in FIG. 1 and previously described, integrated circuits,such as DRAM semiconductor device structures, typically includetransistor gates 12 formed on the surface 16 a of the semiconductorsubstrate 16. In addition to capacitor containers 22, semiconductordevice structures typically also include contact apertures (not shown)formed in the structural layer 20, generally by etching the structurallayer 20. Like capacitor containers 22, contact apertures are typicallycylindrical cavities formed contiguous with a conductive plug 11 (or anactive device region 14 of the semiconductor substrate 16). Throughthese contact apertures, digit lines (not shown) can contact the sourceor drain regions (not shown) of the transistor formed in thesemiconductor substrate 16, as desired.

[0013] As is apparent, if the height of a capacitor container 22 isincreased to maintain the necessary capacitance, the height of thecontact apertures (not shown) similarly must increase. However, due toreduced die sizes and increased feature densities, this height increasemust occur without increasing the width (or diameter) of the contactaperture. However, as contact apertures typically are etched, formationof a large height-to-width ratio is limited by the limitations ofselective etching, as previously described.

[0014] Based upon the above, the inventor has recognized that asemiconductor device structure and method for manufacturing suchstructure that has one or more capacitor containers, contact apertures,or other openings therein with increased height-to-width ratios overthose which may be formed using conventional techniques would bedesirable. Further, the inventor has recognized that a semiconductordevice structure having one or more capacitor containers, contactapertures, or other openings therein with increased aspect ratios thatis simple to manufacture and does not interfere significantly withexisting manufacturing processes would be advantageous.

BRIEF SUMMARY OF THE INVENTION

[0015] The present invention includes semiconductor device structuresand methods of making such structures that include one or more etchedopenings therein with increased height-to-width ratios, or aspectratios. The structures of the present invention are formed by successivelayer deposition wherein etching is affected, generally in a step-wisefashion, as the height of the semiconductor device structure isincreased.

[0016] The present invention further includes semiconductor devicestructures and methods of making such structures that include one ormore capacitor containers, contact apertures, or other openings thereinhaving increased aspect ratios. The semiconductor device structures areformed by stacking an interlayer or cover layer atop a first structurallayer and, subsequently, stacking a second structural layer atop thecover layer. Stepwise etching of capacitor containers, contactapertures, or other openings in the first and second structural layersand the cover layer provides increased height-to-width ratios of theresultant capacitor containers, contact apertures, or other openings.

[0017] Further, the present invention includes semiconductor devicestructures and methods of making such structures in which capacitorcontainers, contact apertures, or other openings having increased aspectratios are formed by deposition of a second structural layer directlyatop an etched first structural layer. Process conditions of thematerial of the second structural layer may be adjusted such thatsubstantial non-conformity and low step coverage are achieved.Subsequent etching of the second structural layer results insemiconductor device structures with one or more capacitor containers,contact apertures, or other openings therein that have increasedheight-to-width ratios relative to those which may be formed usingcurrently known techniques.

[0018] Additionally, the present invention includes a method forself-aligning openings in substantially vertically stacked structurallayers of a semiconductor device structure. Etching of the structurallayers, generally in a stepwise fashion, may result in semiconductordevice structures having openings therein with increased aspect ratios.

[0019] Additional aspects of the invention, together with the advantagesand novel features pertaining thereto, will be set forth in thedescription which follows and will also become readily apparent to thoseof ordinary skill in the art upon examination of the following and fromthe practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the accompanying drawings which form a part of thespecification and are to be read in conjunction therewith:

[0021]FIG. 1 is a schematic illustration of a prior art partiallyfabricated semiconductor device structure for use in integrated circuitssuch as DRAM semiconductor devices.

[0022]FIG. 2 is a schematic illustration of a semiconductor devicestructure having a plurality of capacitor containers therein. Thesemiconductor substrate, conductive structure and insulating layer arenot shown in detail for the sake of simplicity and ease of description.However, it will be understood by those of ordinary skill in the artthat the semiconductor device structure schematically illustrated hereinmay be of any conventional design, having all the components andmaterials so associated.

[0023]FIGS. 3A-3D schematically illustrate the formation of asemiconductor device structure having one or more capacitor containerstherein with increased height-to-width ratios in accordance with anembodiment of the present invention.

[0024]FIGS. 3E-3G schematically illustrate the formation of asemiconductor device structure having one or more capacitor containerstherein with increased height-to-width ratios in accordance with anotherembodiment of the present invention.

[0025]FIG. 4A is an electron micrograph of a semiconductor devicestructure in accordance with the teachings of the present inventiontaken in cross section at a central location of the semiconductorsubstrate. The electron micrograph illustrates that the cover layergenerally remains on the surface of the structural layer and does notsubstantially fill the capacitor container.

[0026]FIG. 4B is an electron micrograph of a semiconductor devicestructure in accordance with the present invention taken in crosssection at a notch of the semiconductor substrate. The electronmicrograph illustrates that the cover layer generally remains on thesurface of the structural layer and does not substantially fill thecapacitor container.

[0027]FIGS. 5A-5J schematically illustrate an exemplary method for theformation of a semiconductor device structure having both a contactaperture and a plurality of capacitor containers therein with increasedaspect ratios.

[0028]FIGS. 6A-6G schematically illustrate another exemplary method forthe formation of a semiconductor device structure having a contactaperture and a plurality of capacitor containers therein with increasedaspect ratios.

[0029]FIGS. 7A-7H schematically illustrate yet another exemplary methodfor forming a semiconductor device structure having both a contactaperture and a plurality of capacitor containers therein with increasedheight-to-width ratios.

[0030]FIGS. 8A and 8B schematically illustrate a self-alignedinterconnection structure and method of forming the same according tothe teachings of the present invention.

[0031]FIG. 9 is an electron micrograph of a semiconductor devicestructure taken in cross section that illustrates the nitride “cap” and“funnel” structures of a self-aligned interconnection structureaccording to the teachings of the present invention.

[0032]FIG. 10 is an electron micrograph of a semiconductor devicestructure taken in cross section that illustrates the alignment ofcapacitor containers formed in stacked structural layers in accordancewith the teachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present invention is directed to semiconductor devicestructures and methods of making such structures that include one ormore capacitor containers, contact apertures, or other openings thereinwith increased height-to-width ratios. The particular embodimentsdescribed herein are intended in all respects to be illustrative ratherthan restrictive. Alternative embodiments will become apparent to thoseof ordinary skill in the art to which the present invention pertainswithout departing from its scope.

[0034] Referring initially to FIG. 2, an exemplary semiconductor devicestructure 10 is shown. The semiconductor device structure of FIG. 2includes a plurality of capacitor container portions 22 a formed in afirst structural layer 20, such as a phosphosilicate glass (PSG) layer,a borosilicate glass (BSG) layer, or a borophosphosilicate glass (BPSG)layer. Conventional techniques for forming a semiconductor devicestructure as depicted in FIG. 2 are known in the art and will not befurther discussed herein. It will be understood that the semiconductordevice structure shown in FIG. 2 further includes at least asemiconductor substrate 16, conductive structure 12 and insulating layer18 underlying the illustrated portion of the structure, as discussedabove in relation to FIG. 1. Such underlying structure is not depictedin FIGS. 2 and 3A-3G for the sake of convenience and ease ofdescription. Capacitor container portions 22 a have a width (ordiameter, as the capacitor container portions may be substantiallycylindrical cavities as previously described), represented herein as Wand first structural layer 20 has a height represented herein as H.

[0035] Using known conventional etching techniques, a maximumheight-to-width ratio of each capacitor container portion 22 a (or otheropening in the structural layer 20) of 7:1 may be achieved whilemaintaining the integrity of the surface underlying the etched layerand, accordingly, the accuracy of the photolithographic image. Thus, theratio of height to width in FIG. 2 cannot exceed 7:1 using conventionaletching techniques. The present invention teaches methods which may beused to overcome this limitation, i.e., for forming semiconductor devicestructures capable of having openings (e.g., capacitor containers 22)therein with aspect ratios greater than 7:1.

[0036] According to the present invention, narrow capacitor containers(i.e., those with increased height-to-width ratios) may be formed bysuccessive deposition of layers. Multiple structural layers 20, 26(e.g., BPSG matrix layers) may be formed substantially vertically on topof one another by stacking a second structural layer 26 substantiallyvertically on top of an etched first structural layer 20 andsubsequently etching into the second structural layer 26 a patternsubstantially identical to the pattern etched in the first structurallayer 20. As is evident, during and subsequent to deposition of thesecond structural layer 26, the integrity of the first structural layer20 should be substantially maintained. That is, any openings (e.g.,capacitor container portions 22 a) in the first structural layer 20should remain substantially devoid of any material therein and the firststructural layer 20 should not be damaged during and subsequent todeposition of the second structural layer 26. To achieve this result, athin cover layer 25, or interlayer, may be deposited on the top surface20 a of the etched first structural layer 20 prior to deposition of thesecond structural layer 26 on top thereof.

[0037] The first cover layer 25 may be deposited using various methodsknown in the art. By way of example and not limitation, chemical vapordeposition (CVD) techniques (such as plasma-enhanced chemical vapordeposition (PECVD)) or physical vapor deposition (PVD) techniques (suchas sputtering) may be used to deposit the first cover layer 25. Thefirst cover layer 25 may be formed of a substantially nonconformingmaterial having low step coverage such that it does not substantiallyspill into any openings (e.g., capacitor container portions 22 a) in thefirst structural layer 20 but, in effect, seals any openings in thefirst structural layer 20 and substantially prevents the material of thesecond structural layer 26 (or any other material) from spilling intothe openings.

[0038] Once the first cover layer 25 has been deposited and seals theopenings (e.g., capacitor container portions 22 a) in the firststructural layer 20, the second structural layer 26 may be deposited onthe top surface 25 a of the first cover layer 25 using any of variousmethods known in the art, such as chemical vapor deposition (CVD),spin-on-glass (SOG), physical vapor deposition (PVD), e.g., such assputtering, and the like. Subsequently, a photoresist layer (not shown)may be deposited on the top surface 26 a of the second structural layer26 and etched to form a photomask (not shown) through which the secondstructural layer 26 may be patterned, as known in the art. By way ofexample, and not limitation, one or more of glow-discharge sputtering,ion milling, reactive ion etching (RIE), reactive ion beam etching(RIBE), plasma etching, point plasma etching, magnetic ion etching,magnetically enhanced reactive ion etching, plasma enhanced reactive ionetching, electron cyclotron resonance and high-density plasma etchingmay be used to form openings (e.g., capacitor container portions 22 b)in second structural layer 26 which provide access to the top surface 25a of first cover layer 25. Utilizing the photoresist (not shown) appliedto the second structural layer 26, a substantially equivalent patternmay be etched into the first cover layer 25 using the same etchant,different etchants, or a combination of etchants. Accordingly, capacitorcontainer portions 22 c are formed in the first cover layer 25 whichsubstantially vertically align with, and may provide access to, thecapacitor container portions 22 a in the first structural layer 20. Thecapacitor container portions 22 c in the first cover layer 25 also alignsubstantially vertically with the capacitor container portions 22 b inthe second structural layer 26. As such, a continuous capacitorcontainer 22 (or other opening) comprised of capacitor containerportions 22 b, 22 c and 22 a may be formed through which access to theunderlying areas of the semiconductor device structure, e.g., activeareas (not shown) of semiconductor substrate 16, may be provided.

[0039] As a photoresist (not shown) is used and patterned to form aphotomask (not shown) that has an image substantially identical to thatutilized to etch the first structural layer 20, etching of the secondstructural layer 26 and the first cover layer 25 creates openings (e.g.,capacitor container portions 22 b and 22 c, respectively) that provideaccess to capacitor container portions 22 a defined by the firststructural layer 20. Thus, the capacitor container portions 22 a, 22 bin the first structural layer 20 and the second structural layer 26,respectively, as well as the container portion 22 c in the first coverlayer 25, may be connected and a semiconductor device structure 10having a capacitor container 22 (or other opening) therein with anincreased aspect ratio may be formed. This process is schematicallyillustrated in FIGS. 3A-3D.

[0040] Fabrication of the first structural layer 20, including alowermost container portion 22 a of at least one capacitor container 22etched therein, may be formed as described above and as shown in FIG. 2.Although the present discussion centers around formation of capacitorcontainers (or contact apertures), it will be understood and appreciatedby those of ordinary skill in the art that the methods of the presentinvention may be used to form semiconductor device structures havingetched openings therein for a variety of applications. All such uses ofthe present technology are intended to be within the scope of thepresent invention.

[0041] After patterning of a photoresist (not shown) to form a photomask(not shown) and etching of the first structural layer 20, a first coverlayer 25 may be deposited on the top surface 20 a of the etched firststructural layer 20, as shown in FIG. 3A. The thickness of the firstcover layer 25 may approximate the widths of the capacitor containers 22so that little material of the first cover layer 25 protrudes into thecapacitor container portions 22 a defined by the first structural layer20 and yet the integrity of the first structural layer 20 may besubstantially maintained during the stacked fabrication of subsequentstructural layers, as more fully described below. The first cover layer25 may be formed of any material,.the process conditions of which arecontrolled such that the material will not substantially conform to thetop surface 20 a of the first structural layer 20. Stated differently,the first cover layer 25 may remain substantially planar and notsubstantially protrude into the container portions 22 a defined by thefirst structural layer 20. By way of example and not limitation, thefirst cover layer 25 may be formed from a high-density plasma (HDP)oxide, a low silane oxide (LSO), a PECVD oxide, an oxide deposited byuse of tetraethylorthosilicate (TVOS), another silicon oxide, siliconnitride, or combinations thereof.

[0042] The first cover layer 25 may be formed by various methods knownin the art. By way of example, and not limitation, chemical vapordeposition (CVD) techniques (such as plasma-enhanced chemical vapordeposition (PECVD)) or physical vapor deposition (PVD) techniques (suchas sputtering) may be used to form the first cover layer 25 by adjustingthe process conditions to achieve poor conformity and poor step coverageso that the deposited material of the first cover layer 25 grows only onthe top surface 20 a of the first structural layer 20. FIGS. 4A and 4Bshow a portion of a semiconductor device structure 10 having a capacitorcontainer 22 therein and a cover layer 25 formed in this manner. FIGS.4A and 4B each show a cross-section of an HDP oxide cover layer 25deposited at low temperature on a capacitor container 22, thesemiconductor device structure 10 having a tungsten nitride (WN) bottomelectrode 28. FIG. 4A shows a cross section taken at a central locationof the semiconductor substrate 16. FIG. 4B shows a cross section takenat a notch of the semiconductor substrate 16. The images clearly showthat the first cover layer 25 covers only the top surface 23 of thecapacitor container 22 and that the material thereof does notsubstantially protrude into the capacitor containers 22.

[0043] As is evident from FIG. 3A, the material of the first cover layer25 is likely to protrude into the capacitor containers 22 to someextent. However, a cover layer 25 formed under process conditions aspreviously described is unlikely to spill into the capacitor containers22 to a depth that exceeds the thickness of the cover layer 25 itself,such thickness represented in FIG. 3A as W.

[0044] As illustrated in FIG. 3B, after the first cover layer 25 hasbeen deposited atop the surface 20 a of first structural layer 20, asecond structural layer 26, formed of a BPSG matrix, or similarmaterial, may be deposited on the top surface 25 a of the first coverlayer 25. Second structural layer 26 may be formed by various methodsknown in the art including, without limitation, chemical vapordeposition (CVD) and the like. Subsequently, a photoresist (not shown)may be applied to the top surface 26 a of the second structural layer 26and patterned to form a photomask (not shown) through which the secondstructural layer 26 may be etched, as known in the art, to formcapacitor container portions 22 b therein through which access to thetop surface 25 a of-first cover layer 25 may be provided. This step isillustrated in FIG. 3C.

[0045] Subsequently, the first cover layer 25 may be separatelypatterned using second structural layer 26 as a mask. Alternatively, thefirst cover layer 25 may not be separately patterned. In any event, thefirst cover layer 25 may be patterned such that access may be providedto the capacitor container portions 22 a defined by the first structurallayer 20. This step is shown in FIG. 3D.

[0046] The etchant or etchants used to etch the second structural layer26 and the first cover layer 25 are, of course, formulated to remove thematerial or materials of these layers and may do so with selectivityover the material or materials of the other layers or structures thatwill be exposed to such etchants. Such processes and etchants are knownin the art. The second structural layer 26 and the first cover layer 25may be etched using the same etchant such that the steps illustrated inFIGS. 3C and 3D occur substantially simultaneously. Alternatively,etchants selective for the various layers may be used such that steps 3Cand 3D occur in a stepwise fashion, as illustrated. Examples ofselective etchants and methods for using the same are disclosed in U.S.Pat. No. 6,117,791, which is hereby incorporated by this reference as ifreproduced in its entirety herein.

[0047] Because a photoresist (not shown) may be used to form a photomask(not shown) that has an image substantially identical to that utilizedto etch the capacitor container portions 22 a in the first structurallayer 20, etching of the second structural layer 26 and the first coverlayer 25 creates openings therein (capacitor container portions 22 b, 22c, respectively) which may provide access to the capacitor containerportions 22 a defined by the first structural layer 20. The result is asemiconductor device structure 10 having capacitor containers 22 withaspect ratios that may be increased substantially over those of asemiconductor device structure having only a single etched structurallayer.

[0048] As best seen in FIG. 3A, the widths (or diameters) of thecapacitor containers 22 may be substantially equal to the thickness offirst cover layer 25. This approximate equivalence may be useful forachieving an increased aspect ratio while still having little or nomaterial of the first cover layer 25 protrude into the capacitorcontainer portions 22 a. Further, as mentioned above, while the materialof the first cover layer 25 may enter the capacitor container portions22 a defined by the first structural layer 20 to some extent, the depthof material inside the container portions 22 a should not exceed thethickness W of the first cover layer 25. Thus, the depth of the materialof first cover layer 25 inside of capacitor container portions 22 ashould not exceed W.

[0049] As previously mentioned, a maximum aspect ratio of about 7:1 maybe achieved using known conventional etching techniques. Because boththe second structural layer 26 and the first cover layer 25 must beetched to connect the capacitor container portions 22 b and 22 c,respectively, to the capacitor container portions 22 a defined by thefirst structural layer 20, as must any material of the first cover layer25 that has protruded into the container portions 22 a of the firststructural layer 20, the combination of the height of the secondstructural layer 26, the thickness of the first cover layer 25, and thedepth that material of the first cover layer 25 extends into containerportions 22 a cannot exceed H. Thus, assuming the thickness of the firstcover layer 25 is about equal to the width W of the capacitor containerportions 22 a formed in first structural layer 20, and that the materialof the first cover layer 25 protrudes into the container portions 22 a adistance of about W, capacitor containers 22 with a height of about 2H-Wmay be formed utilizing known conventional etching techniques and thelayered fabrication methods of the present invention. Such a capacitorcontainer 22 would have a height-to-width ratio of about 2H-W:W. Thus,for example, if W=1 and H=7 (the approximate maximum aspect ratiocondition available using current etching techniques), a capacitorcontainer 22 with an aspect ratio of 13:1 may be achieved by forming asecond structural layer 26 atop the first structural layer 20 using theteachings of the present invention.

[0050] As will be understood and appreciated by those of ordinary skillin the art, this technique theoretically could be repeated for anunlimited number of structural layers creating capacitor containershaving very large aspect ratios. For instance, formation of a secondcover layer and third structural layer would result in a maximum aspectratio of 3H-2W:W or 19:1. Similarly, formation of a third cover layerand fourth structural layer would result in a maximum aspect ratio of4H-3W:W or 25:1.

[0051] In another embodiment, a second structural layer 26 may bedeposited directly atop the first structural-layer 20 by adjusting theprocess conditions thereof, as known in the art, to achieve poorconformity and poor step coverage employing a known depositiontechnology, such as those discussed above with regard to the depositionof the first cover layer 25. If the process conditions of the secondstructural layer 26 are adjusted in this manner, the second structurallayer 26 may be deposited directly onto the top surface 20 a of etchedfirst structural layer 20 without the need for a first cover layer 25,as the material of the second structural layer 26 would notsubstantially protrude into the capacitor container portions 22 adefined by first structural layer 20. Using this alternative process,semiconductor device structures may be fabricated in fewer process stepsthan as described above in reference to FIGS. 3A-3D, as there would notbe one or more separate cover layers 25 to be fabricated or etched. Thisembodiment is illustrated in FIGS. 3E-3G.

[0052] As previously discussed, and as shown in FIG. 1, integratedcircuits, such as DRAM semiconductor devices 10, typically includetransistor gates 12 built on the surface 16 a of a semiconductorsubstrate 16, e.g., a silicon (Si) wafer. Accordingly, in addition tocapacitor containers 22, semiconductor devices also typically includecontact apertures 30 (not shown) formed through an insulating layer 18(e.g., a BPSG layer) through which protective conductive plugs 11 mayextend to electrically connect the digit lines and the source or drainregions of the transistors, as desired. Alternatively, contact apertures30 may be formed to electrically connect digit lines with active deviceregions 14 of the semiconductor substrate 16 in the absence ofconductive plugs 11.

[0053] If the height of a semiconductor device structure is increasedaccording to the teachings of the present invention, the heights of thecontact apertures must similarly increase. However, due to the trend inthe semiconductor industry of reduced die sizes, it may be desirable forthis height increase to occur without increasing the widths (ordiameters) of the contact apertures 30. However, as contact apertures 30are typically etched, forming apertures with large height-to-widthratios is limited by conventional etching techniques, just as it waslimited with regard to capacitor containers 22.

[0054] The methods of the present invention may be employed to formcontact apertures 30 with increased aspect ratios as well as to formcapacitor containers 22, as previously described. In semiconductordevice structures having both capacitor containers 22 and contactapertures 30, it may be desirable to form such features simultaneouslyor in a stepwise fashion. FIGS. 5-7 schematically illustrate variousmethods of forming semiconductor device structures, such as DRAMsemiconductor devices, according to the methods of the presentinvention.

[0055] In each of FIGS. 5-7, a semiconductor substrate 16, e.g., asilicon (Si) wafer, having a plurality of active device regions 14 (orsource/drain regions) which typically comprise conductively dopedregions of the semiconductor substrate 16 is formed and covered with aninsulating layer 18, such as a borophosphosilicate glass (BPSG) layer,as previously described. If desired, semiconductor substrate 16 may alsoinclude conductive plugs 11 located between neighboring conductivestructures 12 to protect the underlying active device regions 14, asshown.

[0056] Referring now to FIG. 5A, in an exemplary method, a firststructural layer 20 (e.g., a BPSG layer) may be deposited atop theinsulating layer 18. Subsequently, a photoresist layer (not shown) maybe applied to the first structural layer 20 and patterned (i.e.,selectively exposed and developed) to form a photomask (not shown). Thefirst structural layer 20 may be etched to form a lowermost portion 30 aof a contact aperture 30 therein. Contact aperture portion 30 a may bepatterned at a location in the first structural layer 20 such that italigns substantially vertically with a conductive plug 11, as shown, oran active device region 14 of the semiconductor substrate 16, ifdesired, and provides access thereto. It will be understood by those ofordinary skill in the art that a portion of the insulating layer 18 mayalso be patterned such that the contact aperture portion 30 a may beexposed to the conductive plug 11 (or active substrate region, ifdesired). It is noted that fabrication of semiconductor devices havingsuch structures is carried out with respect to multiple contactapertures 30 and multiple capacitor containers 22 substantiallysimultaneously. However, for sake of clarity, only one such contactaperture 30 and its relation to capacitor containers 22 on either sidethereof is depicted in the figures.

[0057] After forming the lowermost portion 30 a of contact aperture 30,a first cover layer 25 (for example, an HDP oxide layer) may bedeposited on the top surface 20 a of the first structural layer 20 tocover the top surface 31 of the contact aperture portion 30 a withoutsubstantially protruding into the contact aperture portion 30 a, asillustrated in FIG. 5B. First cover layer 25 may be formed substantiallyas discussed above with reference to FIG. 3B. It is noted that whileFIGS. 5A-5J are not shown to scale, the width of contact apertureportion 30 a and the thickness of first cover layer 25 closelyapproximate one another, as previously discussed, with respect to thethickness of the first cover layer 25 and the width of the containerportion 22 a depicted in FIG. 3B. Further, while not shown herein, it islikely that material from the first cover layer 25 will protrude intothe contact aperture portions 30 a or other openings in the firststructural layer 20 to some extent, as described above.

[0058] Subsequent to application of the first cover layer 25, the coverlayer 25 may be patterned to form the container portion 22 c of one ormore capacitor containers 22. Such patterning may also be effectedthrough first structural layer 20. Again, it will be understood that aportion of insulating layer 18 may also be etched such that eachcapacitor container portion 22 a is exposed to a conductive plug 11. Bypatterning contact aperture 30 and capacitor containers 22 in a stepwisefashion as shown in FIGS. 5A-5C, the contact aperture portion 30 aremains substantially sealed during deposition and etching of the secondstructural layer 26, as well as through the formation of the capacitors32, as more fully described below.

[0059] As shown in FIG. 5D, a second structural layer 26 maysubsequently be deposited on the top surface 25 a of the first coverlayer 25. Again, the second structural layer 26 may be deposited by anyof various methods known in the art including, without limitation, CVDand the like. Alternatively, the need for a first cover layer 25 may beeliminated by preventing the material of the second structural layer 26from substantially protruding into the capacitor container portions 22a, the deposition conditions of the second structural layer 26 beingadjusted to achieve poor conformity and poor step coverage, aspreviously described.

[0060] Next, a photoresist layer (not shown) may be deposited on the topsurface 26 a of the second structural layer 26 and patterned to form aphotomask (not shown) and the second structural layer 26 may bepatterned to form capacitor container portions 22 b therein. As aphotoresist (not shown) may be used that has an image substantiallyidentical to that employed to pattern the first cover layer 25, etchingof the second structural layer 26 may provide access to the capacitorcontainer portions 22 a defined by the first structural layer 20. Thisstep is shown in FIG. 5E. The result is a semiconductor device structure10 having capacitor containers 22 therein with increased height-to-widthratios.

[0061] Subsequently, as shown in FIG. 5F, capacitors 32 may be formed ineach of the capacitor containers 22 by depositing a layer 33 of anysuitable conductive material (e.g., a conductively doped hemisphericalgrain (HSG) polysilicon layer) on the interior sidewalls 24 of thecontainer 22, followed by deposition of a dielectric layer 34 andanother conductive layer 35, as known in the art. Next, a photoresistlayer (not shown) may be applied and patterned to form a photomask (notshown) on the top surface 26 a of the second structural layer 26 and thesecond structural layer 26 may be etched to form a contact apertureportion 30 b of at least one contact aperture 30 therein. The firstcover layer 25 may be patterned using the same etchant, differentetchants, or a combination of etchants, as previously described. As aphotoresist (not shown) is used and pattered to form a photomask (notshown) in this instance that has an image substantially identical tothat utilized to form the contact aperture portion 30 a through firststructural layer 20, etching of the second structural layer 26 and thefirst cover layer 25 creates openings which provide access to thecontact aperture portion 30 a. This step is illustrated in FIG. 5G. Theresult is a contact aperture 30 with an increased aspect ratio relativeto that which previously could be achieved using conventional selectiveetching techniques.

[0062] Subsequently, a second cover layer 36 may be deposited on top ofetched second structural layer 26 to shield the capacitor containerportions 22 c (not shown) formed in the first cover layer 25 fromsubsequent processes. Again, while not shown to scale, it will beunderstood that the second cover layer 36 has a thickness which closelyapproximates the width of the capacitor containers 22 and the contactapertures 30, as previously discussed. The second cover layer 36 may beformed of materials and using methods as previously described withregard to first cover layer 25. A third structural layer 37 may then bedeposited, for instance, by CVD, PVD, or the like, on the top surface 36a of the second cover layer 36, as shown in FIG. 5H.

[0063] Next, the third structural layer 37 may be etched as known in theart (e.g., by mask and etch processes) to form a contact apertureportion 30 d therein. The second cover layer 36 may also be etched usingeither the same etchant, a different etchant, or a combination ofetchants, as previously described, to form contact aperture portion 30e. In this instance, a photoresist (not shown) may be used and patternedto form a photomask (not shown) that has an image substantiallyidentical to that employed to pattern and etch the contact apertureportions 30 a, 30 b and 30 c, respectively, into the first structurallayer 20, the second structural layer 26 and the first cover layer 25.Thus, this etching step provides access to the contact aperture portions30 a and results in a contact aperture 30 having an even furtherincreased aspect ratio. This step is-shown in FIG. 5I.

[0064] Finally, as shown in FIG. 5J, a conductive metal, such astungsten, may be deposited into contact aperture 30 to form a conductiveplug 38 and a conventional metal 39 may be deposited atop a portion ofthe third structural layer 37 to electrically connect the conductiveplug 38 and from which digit lines (not shown) are subsequently formed.Such processes are known to those of ordinary skill in the art and willnot be further discussed herein.

[0065] In another embodiment, the conductive metal, e.g., tungsten, maybe deposited in the contact aperture 30 in stepwise fashion as thevarious portions 30 a, 30 b, 30 c, 30 d, 30 e of the contact aperture 30are patterned and etched. This method may be desirable if the processesof the memory capacitor will affect the stability of the contactapertures 30 as they exist in the system.

[0066] Referring now to FIGS. 6A-6G, in another exemplary method offorming semiconductor device structures 10 having both contact apertures30 and capacitor containers 22, a first structural layer 20 (e.g., aBPSG layer) may be initially deposited on the top surface 18 a of aninsulating layer 18 that surrounds the active device regions 14 of asemiconductor substrate 16, as previously described. Subsequently, aphotoresist layer (not shown) may be deposited on the top surface 20 aof the first structural layer 20 and patterned to form a photomask (notshown). The first structural layer 20 may be patterned to form alowermost portion 30 a of at least one contact aperture 30 therein, aswell as the lowermost portions 22 a of capacitor containers 22 on eitherside thereof. The contact aperture portion 30 a and the capacitorcontainer portions 22 a may be etched at a location in the firststructural layer 20 such that each aligns substantially vertically withan active device region 14 of the semiconductor substrate 16 (or aconductive plug 11, if desired) and provides access thereto. It wilt beunderstood by those of ordinary skill in the art that a portion of theinsulating layer 18 also may be patterned such that the lowermostportion 30 a of the contact aperture 30 and the lowermost portions 22 aof the capacitor containers 22 may be exposed to the respectiveconductive plugs 11 (or active device region 14, if desired). It isagain noted that fabrication of semiconductor device structures withsuch features is typically carried out with respect to multiple contactapertures 30 and multiple capacitor containers 22 substantiallysimultaneously. However, for the sake of clarity, only one such contactaperture 30 and its relation to capacitor containers 22 on either sidethereof are depicted in the figures.

[0067] After forming the lowermost portion 30 a of the contact aperture30 and the lowermost portions 22 a of the capacitor containers 22, afirst cover layer 25 (e.g., an HDP oxide layer) may be deposited on thetop surface 20 a of the etched first structural layer 20 as previouslydescribed, followed by deposition of a second structural layer 26. Thesecond structural layer 26 may be deposited on the top surface 25 a ofthe first cover layer 25 by any of various methods known in the artincluding, without limitation, CVD, PVD and the like. It is noted thatwhile FIGS. 6A-6G are not shown to scale, the width of the contactaperture portion 30 a, the widths of the capacitor container portions 22a and the thickness of the first cover layer 25 may closely approximateone another, as previously discussed.

[0068] Next, a photoresist layer (not shown) may be deposited on the topsurface 26 a of the second structural layer 26 and patterned to form aphotomask (not shown). The second structural layer 26 may then be etched(e.g., by conventional etching techniques) to form portions 22 b, 30 bof respective capacitor containers 22 and contact apertures 30 therein.First cover layer 25 may also be etched using the same etchant,different etchants, or a combination of etchants, as previouslydescribed, to form portions 22 c and 30 c of capacitor containers 22 andcontact apertures 30, respectively. As a photoresist (not shown) is usedand patterned to form a photomask (not shown) that has an imagesubstantially identical to that utilized to pattern the first structurallayer 20, etching of the second structural layer 26 and the first coverlayer 25 provides access to the capacitor container portions 22 a andthe contact aperture portions 30 a defined by the first structural layer20. The result is a semiconductor device structure having both a contactaperture 30 and capacitor containers 22 with increased aspect ratios, asshown in FIG. 6A.

[0069] Subsequently, as shown in FIG. 6B, a second cover layer 36 may bedeposited atop the surface 26 a of the second structural layer 26 usingmethods previously described. The second cover layer 36 may be formed ofmaterials and by process conditions such that it has a low conformityand low step coverage similar to the first cover layer 25. Again, itwill be understood that while FIGS. 6B-6G are not shown to scale, thethickness of the second cover layer 36 may closely approximate thewidths of the contact aperture 30 and the capacitor containers 22, aspreviously discussed.

[0070] Subsequent to deposition of the second cover layer 36, the secondcover layer 36 may be patterned to provide access to the capacitorcontainer portions 22 a. A photoresist (not shown) may be used in thisinstance to form a photomask (not shown) which, along with a suitableetchant, provides the container portions 22 d in the second cover layer36 at locations substantially vertical to the capacitor containerportions 22 b while leaving the contact aperture portion 30 bsubstantially shielded. Thus, patterning of the second cover layer 36provides access to the capacitor container portions 22 a, 22 b but notto the contact aperture portions 30 a, 30 b. This step is shown in FIG.6C.

[0071] Next, as shown in FIG. 6D, capacitors 32 may be formed in each ofthe capacitor containers 22 by depositing a layer 33 of any suitableconductive material (e.g., a conductively doped hemispherical grain(HSG) polysilicon layer) on the interior sidewalls 24 of the capacitorcontainers 22, followed by deposition of a dielectric layer 34 andanother conductive layer 35, as known in the art. Subsequently, a thirdstructural layer 37 may be deposited on the top surface 36 a of theetched second cover layer 36 using any of various methods known in theart including, without limitation, CVD, PVD and the like. This step isillustrated in FIG. 6E.

[0072] Subsequently, the third structural layer 37 may be etched to formcontact aperture portion 30 d therein. Though a separate photomask maynot be used, second cover layer 36 may also be etched using the sameetchant, different etchants, or a combination of etchants, as previouslydescribed. In this instance, a photoresist (not shown) may be used andpatterned to form a photomask (not shown) which provides an opening,which comprises a portion 30 d of the contact aperture 30 in the thirdstructural layer 37 and a portion 30 e of the contact aperture 30 insecond cover layer 36 at a location substantially vertical to contactaperture portions 30 a and 30 b. Thus, patterning of the third coverlayer 37 and the second cover layer 36 provides access to the contactaperture portions 30 a, 30 b 30 c. This step is shown in FIG. 6F.

[0073] Finally, as shown in FIG. 6G, a conductive metal, such astungsten, may be deposited into contact aperture 30 to form a conductiveplug 38 and a conventional metal 39 may be deposited atop a portion ofthe third structural layer. 37 to electrically connect the conductiveplug 38 and from which digit lines (not shown) are subsequently formed.Such processes are known to those of ordinary skill in the art and willnot be further discussed herein.

[0074] In an alternative embodiment, the conductive metal, e.g.,tungsten, may be deposited in the contact aperture 30 in stepwisefashion as the various portions 30 a, 30 b, 30 c, 30 d, 30 e of thecontact aperture 30 are formed. This method may be employed where thesubsequent processes for fabricating the capacitors 32 will affect thestability of the contact apertures 30 as they exist in the system.

[0075] In yet another method of forming semiconductor device structures10 having both contact apertures 30 and capacitor containers 22, a firststructural layer 20 (e.g., a BPSG layer) may be deposited on the topsurface 18 a of an insulating layer 18 that surrounds the active deviceregions 14 of a semiconductor substrate 16, as previously described.Subsequently, a photoresist layer (not shown) may be deposited on thetop surface 20 a of the first structural layer 20 and patterned to forma photomask (not shown). The first structural layer 20 then may beetched to form a lowermost portion 30 a of at least one contact aperture30 therein, as well as the lowermost portions 22 a of capacitorcontainers 22 on either side of contact aperture portion 30 a. Both thecontact aperture portion 30 a and the capacitor container portions 22 amay be etched at locations in the first structural layer 20 such thateach substantially aligns with a conductive plug 11 or an active deviceregion 14 of the semiconductor substrate 16, as desired, and providesaccess thereto. This is illustrated in FIG. 7A. It will be understoodthat a portion of the insulating layer 18 also may be patterned suchthat the contact aperture portion 30 a and capacitor container portions22 a may be exposed to the conductive plug 11 (or active device region14, if desired). Further, it is again noted that fabrication ofsemiconductor device structures having such features is typicallycarried out with respect to multiple contact apertures 30 and multiplecapacitor containers 22 substantially simultaneously. However, for thesake of clarity, only one such contact aperture portion 30 a and itsrelation to capacitor container portions 22 a on either side of thecontact aperture portion 30 a are depicted in FIGS. 7A-7H.

[0076] As illustrated in FIG. 7B, subsequent to forming the contactaperture portion 30 a and the capacitor container portions 22 a, a firstcover layer 25 (for example, an HDP oxide layer) may be deposited on thetop surface 20 a of the etched first structural layer 20, as previouslydescribed. It is noted that while FIGS. 7A-7H are not shown to scale,the width of contact aperture portion 30 a, the widths of capacitorcontainer portions 22 a and the thickness of first cover layer 25 mayclosely approximate one another, as previously discussed.

[0077] Subsequently, a second structural layer 26 may be deposited onthe top surface 25 a of the first cover layer 25 by any of variousmethods known in the art, e.g., CVD. Next, a photoresist layer (notshown) may be deposited on the top surface 26 a of the second structurallayer 26 and patterned (e.g., by conventional etching techniques) toform a photomask (not shown) through which the capacitor containerportions 22 b may be etched. The first cover layer 25 may also be etchedusing the same etchant, different etchants, or a combination ofetchants, as previously described, to form container portions 22 c. Inthis instance, a photoresist (not shown) may be used and patterned toform a photomask (not shown) that provides capacitor container portions22 b oriented substantially vertical to capacitor container portions 22a defined by the first structural layer 20. Thus, etching of the secondstructural layer 26 and the first cover layer 25 provides access to thelowermost portions 22 a of the capacitor containers 22. The result iscapacitor containers 22 having increased aspect ratios. This isillustrated in FIG. 7C.

[0078] Subsequently, as shown in FIG. 7D, capacitors 32 may be formed ineach of the capacitor containers 22 by depositing a layer 33 of anysuitable conductive material (e.g., a conductively doped hemisphericalgrain (HSG) polysilicon layer) on the interior sidewalls 24 of eachcapacitor container 22, followed by deposition of a dielectric layer 34and another conductive layer 35, as known in the art. Subsequently, adifferent photoresist may be applied to the top surface 26 a of secondstructural layer 26 and patterned with an image that provides an openingin the second structural layer 26 that comprises an upper portion 30 bof the contact aperture 30 and provides access to the lowermost portion30 a of the contact aperture 30. It will be understood that first coverlayer 25 may also be patterned to form contact aperture portion 30 c foraccess to contact aperture 30 to be effected. This may be accomplishedby using the same etchant, different etchants, or a combination ofetchants, as previously discussed. The result is a contact aperture 30having an increased aspect ratio as shown in FIG. 7E.

[0079] Next, as shown in FIG. 7F, a second cover layer 36 may bedeposited on the top surface 26 a of second structural layer 26. Thesecond cover layer 36 may be formed of materials and by processconditions such that it has a low conformity and low step coverage,similar to that of first cover layer 25. Again, it will be understoodthat while FIGS. 7F-7H are not shown to scale, the thickness of thesecond cover layer 36 may closely approximate the widths of the contactaperture 30 and the capacitor containers 22, as previously discussed.

[0080] Subsequently, a third structural layer 37 may be deposited atopthe second cover layer 36, for instance, by CVD, PVD, or the like. Aphotoresist (not shown) may be used and patterned to form a photomask(not shown) through which an opening may be formed in the thirdstructural layer 37, which opening comprises another upper portion 30 dof the contact aperture 30. The second cover layer 36 may also be etchedusing the same etchant, different etchants, or a combination ofetchants, as previously described, to form portion 30 e of contactaperture 30. In this instance, a photoresist (not shown) may be utilizedand patterned to form a photomask (not shown) that has an imagesubstantially identical to that used to form the contact apertureportion 30 b in the second structural layer 26 and the contact apertureportion 30 c in the first cover layer 25. Thus, patterning of the thirdstructural layer 37 and the second cover layer 36 provides access to thelower portions 30 a, 30 b, 30 c of the contact aperture 30. This step isillustrated in FIG. 7G. The result is a contact aperture 30 having aneven further increased aspect ratio.

[0081] Subsequently, as shown in FIG. 7H, a conductive metal, such astungsten, may be deposited at least into contact aperture 30 to form aconductive plug 38 therein. The conductive metal may also be patternedto form digit lines (not shown) or another metal 39 may be depositedatop at least a portion of third structural layer 37 and patterned toform digit lines. Such processes are known to those of ordinary skill inthe art and will not be discussed further herein.

[0082] In an alternative embodiment, the conductive metal, e.g.,tungsten, may be deposited in the contact aperture 30 in stepwisefashion as the various portions 30 a, 30 b, 30 c, 30 d, 30 e of thecontact aperture 30 are formed. This method may be employed where thesubsequent processes for fabricating the capacitor 32 will affect thestability of the contact apertures 30.

[0083] One potential difficulty in manufacturing contact apertures 30,capacitor containers 22 and other semiconductor device structures havingopenings etched therein with increased aspect ratios according to themethods of the present invention is the alignment of the capacitorcontainers 22, the contact apertures 30, or other openings formed in thesecond (or third, etc.) structural layer 26 to those formed in the first(or second, etc.) structural layer 20. In order to minimize offset ofthe alignment in the photolithography and etching procedures, themethods of the present invention may be self-aligning, which may ensurecommunication between the upper portions of the capacitor containers 22and/or the upper portions of the contact apertures 30 and the lowerportions of the capacitor containers 22 and/or contact apertures 30.

[0084] Self-aligned interconnection in accordance with teachings of thepresent invention may be effected by use of selective etch processes,for example, the use of etchants or etchant mixtures which removesilicon oxide over silicon nitride. For this reason, a suitable materialfrom which a self-aligned interconnection structure may be formed for astructural layer comprised of BPSG is silicon nitride because thenecessary selective etch processes already exist in the semiconductorindustry and are widely used. These processes are more fully describedbelow. As will be understood and appreciated by those of ordinary skillin the art, other materials may be used to facilitate self-alignedinterconnection in accordance with the teachings of the presentinvention, depending upon the materials from which the structural layersthemselves are formed.

[0085] The process of forming a self-aligning interconnection structurein accordance with teachings of the present invention is described andillustrated in FIGS. 8A and 8B. Initially, a first structural layer 20(FIGS. 3A-3D and 5A-7H) having one or more capacitor containers 22and/or contact apertures 30 therein is formed, as previously described.An exemplary structure having a structural layer 20 with a plurality ofcapacitor containers 22 etched therein is shown in FIG. 8A. It will beunderstood by those of ordinary skill in the art that the semiconductordevice structures schematically illustrated herein may be of anyconventional design, having all of the components and materials soassociated.

[0086] Subsequently, as shown in FIG. 8B, a layer 43 comprising amaterial (e.g., silicon nitride) that is removed at a slower rate than amaterial (e.g., silicon dioxide) of a next higher layer (not shown) isdeposited on top of the structural layer 20 so as to partially, but notfully, cover the openings (e.g., capacitor containers 22) therein. Anopening through layer 43 is located substantially vertically above eachopening in the structural layer 20 and has a dimension small enough tosubstantially prevent material of a subsequently deposited, next-higherstructural layer (not shown) from being introduced into the openings.Thus, cap-shaped nitride structures, referred to herein as nitride caps44, serve the functions of the first cover layer 25 or interlayer, aspreviously described. As such, utilizing the present method alleviatesthe need to provide a separate cover layer atop a lower etchedstructural layer.

[0087] Layer 43 may be deposited by any of various methods known in theart, including, without limitation, known PECVD nitride processes. Basedupon the geometric limitations of structural layer 20 having one or moreopenings (e.g., capacitor containers 22) therein, process conditions maybe controlled to produce a layer 43 so as to include nitride caps 44,which reside on top of remaining portions of the structural layer 20.Nitride caps 44 residing on opposite sides of an opening (e.g.,capacitor container 22) of a structural layer 20 form a sort of funnelstructure 46, the apex of which points toward the center (represented inFIG. 8B as line C) of the openings etched in the structural layer 20.This funnel structure 46 is shown by dashed line in FIG. 8B. As thefunnel structure 46 is formed in situ and determined by the position ofthe opening (e.g., capacitor container 22 or contact aperture 30, asappropriate), the apex of the funnel structure 46 self-aligns toward thecenter of the opening. The funnel structure 46 will then facilitatealignment of openings formed in the next-higher structural layer (notshown) with those of the structural layer 20, the next-higher structurallayer being deposited on top of the nitride caps 44 using any of themethods previously described.

[0088] To achieve a structure having openings (e.g., capacitorcontainers 22, contact apertures 30, or other openings) with increasedaspect ratios, an etching process selective to the nitride cap 44 may beused. In a first step, the next-higher structural layer (not shown) maybe etched with an etchant selective for the oxide material (e.g., BPSG)of the structural layer itself. This etchant will selectively stop atthe nitride cap 44. Subsequently, in a second step, the nitride cap 44may be etched with a different etchant (or combination of etchants) thatis selective for the nitride cap 44 without over-etching of thestructural layer.

[0089] The electron micrograph cross-sectional image shown in FIG. 9illustrates the nitride cap 44 and funnel structures 46 on asemiconductor substrate 16. The image clearly shows the conceptdescribed in FIG. 8B. Further, as shown in FIG. 10, when a second etchis performed to form the next-higher layer of openings (e.g., capacitorcontainers 22 or contact apertures 30, as appropriate), the etchantstops at the nitride cap 44. Although the etch process was not completedin the micrograph of FIG. 10, it can be clearly seen that the top andbottom container portions 22 b, 22 a are in substantial alignment. Withanother etchant (or combination of etchants) to etch the nitride cap 44,the upper capacitor container portions 22 b (and/or contact apertureportions 30 b) and the bottom container portions 22 a (and/or contactaperture portions 30 a) will become connected to form capacitorcontainers 22 (and/or contact apertures 30) having an increased aspectratio.

[0090] Carried out as previously described, the teachings of the presentinvention offer a number of advantages over conventional technology.First, decreasing die sizes and the limitations of current etchtechnology will no longer limit the widths of capacitor containers,contact apertures, or other openings in semiconductor substrates.Accordingly, adequate capacitance may still be achieved despite areduction in the widths of such openings. Second, the methods describedherein are scalable. Stated another way, the smaller the openings (e.g.,contact apertures, capacitor containers, or other openings), the moreadvantages the teachings of the present invention provide. Further, themethod for self-alignment provides a large margin for thephotolithography and etching processes to align two or more structurallayers to create capacitor containers, contact apertures, or otheropenings in a semiconductor substrate having increased height-to-widthratios.

[0091] In conclusion, the present invention is directed to fabricationof semiconductor devices having capacitor containers, contact apertures,or other recessed features with increased height-to-width ratios.Further, the present invention relates to methods of formingsemiconductor device structures having capacitor containers, contactapertures, or other recessed features with increased aspect ratios.Still further, the present invention is directed to methods of aligningmultilayered semiconductor device structures to create a structurehaving dimensions as close to the design requirements as possible.

[0092] The present invention has been described in relation toparticular embodiments that are intended in all respects to beillustrative rather than restrictive. Alternative embodiments willbecome apparent to those skilled in the art to which the presentinvention pertains without departing from its scope.

What is claimed is:
 1. A semiconductor structure comprising: a firststructural layer positioned on an active surface of a semiconductorsubstrate, said first structural layer having a first substantiallyvertical opening portion therein; and a second structural layerpositioned substantially vertically above said first structural layer,said second structural layer having a second substantially verticalopening portion therein; wherein said first opening portion and saidsecond opening portion are in substantial vertical alignment to form acontiguous opening in said semiconductor structure, said contiguousopening having a height-to-width ratio in excess of 7:1.
 2. Thesemiconductor structure of claim 1, wherein said first structural layeris in contact with at least one of an active device region and aconductive plug formed on said semiconductor substrate.
 3. Thesemiconductor structure of claim 1, wherein said first structural layercomprises at least one of a phosphosilicate glass structural layer, aborosilicate glass structural layer, and a borophosphosilicate glassstructural layer.
 4. The semiconductor structure of claim 1, whereinsaid second structural layer comprises at least one of a phosphosilicateglass structural layer, a borosilicate glass structural layer, and aborophosphosilicate glass structural layer.
 5. The semiconductorstructure of claim 1, wherein said contiguous opening, comprises atleast one of a contact aperture and a capacitor container.
 6. Thesemiconductor structure of claim 1, further comprising: a cover layerpositioned substantially vertically above said first structural layerand substantially vertically below said second structural layer, saidcover layer having a substantially vertical connecting opening portiontherein; wherein said connecting opening portion is in substantialvertical alignment with said first opening portion and said secondopening portion to form said contiguous opening in said semiconductorstructure.
 7. The semiconductor structure of claim 6, wherein acombination of said second opening portion and said connecting openingportion forms a combined opening portion having a maximumheight-to-width ratio of 7:1.
 8. The semiconductor structure of claim 6,wherein said cover layer has a height which is substantially equivalentto a width of said contiguous opening.
 9. The semiconductor structure ofclaim 6, wherein said cover layer comprises at least one of ahigh-density plasma oxide cover layer, a low silane oxide cover layer, aplasma-enhanced chemical vapor deposition oxide cover layer, an oxidelayer grown from tetraethylorthosilicate, a silicon nitride cover layer,and a silicon oxide cover layer.
 10. The semiconductor structure ofclaim 6, wherein said cover layer comprises a self-aligninginterconnection structure that facilitates substantially verticalalignment of said first opening portion and said second opening portion.11. A structure for a semiconductor device having at least onesubstantially vertical opening therein, said substantially verticalopening having a height-to-width ratio in excess of 7:1.